Of course, the ancient Greek astronomer Aristarchus of Samos (310-230 BCE) came up with a heliocentric theory of the solar system long before Copernicus or this fictional Da Vinci, and it would have been nice to see Da Vinci, who has been portrayed as very well versed in the classics, at least mention Aristarchus in this episode. But the narrative was nonetheless well played.
Da Vinci already correctly sees that the Earth is round, not flat, as did many of the most knowledgeable thinkers of his day, including Columbus. He tries to explain this to the uneducated people on the ship he commandeered for the voyage west, and pins his argument on what he thinks the planet Venus will look like in the sky. But Venus does not look the way Da Vinci expects - because his expectation is based on Ptolemy's model of the planets revolving around the Earth, not Aristarchus's that the planets revolve around the sun - and this gets Da Vinci into hot water out on the sea. His realization that the planets revolve not around the Earth but the Sun is too late to save most of his frightened shipmates, who kill themselves rather than risk falling off the edge of the Earth, but at least Da Vinci will have more accurate cosmic bearings from now on.
So we once again get a good lesson in the history of science tied into Da Vinci's adventure. Meanwhile, back in Italy, we have two good continuing stories. In one, Lorenzo makes his way on the road to redeem his city of Florence. In the other, we learn the truth about the evil Pope and his imprisoned brother, in an instructive series of flashbacks.
So far, I'm enjoying this second season of Da Vinci's Demons much more than the first, because of the second's grounding in science, and I'm now looking forward to Da Vinci's arrival in the New World.
See also Da Vinci's Demon's 2.1: Science Fiction v Fantasy ... Da Vinci's Demons 2.2: Renaissance Radio ... Da Vinci's Demons 2.3: Submarine
what some other ancient Greeks were thinking in the time of Aristarchus